Electrodes for arc discharge valves



Patented Mar. 21, 1939 UNITED STATES PATENT OFFICE Hugo J. Seemann, Berlin-Steglitz, Germany, assignor to General Electric Company, a corporation of New York No Drawing. Application May 19, 1938, Serial No. 208,930. In Germany May 26, 1937 8 Claims.

My invention relates to electrodes for arc discharge valves, and more particularly to such valves in which an arc is periodically ignited and extinguished between a pair of electrodes and a continuous fiow of some fluid medium is maintained between the electrodes.

Electric valves of the kind referred to have been described in a book by Erwin Marx entitled Lichbogenstromrichter, published in Berlin in 1932, and in the United States Letters Patent No. 2,074,930, granted March 23, 1937 upon the application of Erwin Marx. In such systems it has been customary to provide a continuous flow of gas, such as air, within the gap between the electrodes. In some of the arrangements the principal pair of electrodes has been provided with an auxiliary electrode which serves as a starting or ignition electrode. After an arc has been started between one of the principal electrodes and the auxiliary electrode the arc was carried over to the other principal electrode. Due to the action of the oxygen in the air the principal electrodes are subject to considerable deterioration and in accordance with my invention this disadvantage is greatly reduced by providing electrodes of an eutectic silver-copper alloy to which has been added a small amount of thorium or barium.

It is, therefore, an object of my invention to provide a new and improved electrode for arc discharge devices which is resistant to deterioration and which has a relatively long life.

It is another object of my invention to provide an electric conductor for electric valves which resists the deteriorating action of an are discharge.

The novel features which are characteristic of my invention are set forth with particularity in the appended claims. My invention itself however, will be best understood from reference to the following specification.

In carrying out my invention, I employ an alloy which consists primarily of silver and copper together with thorium or barium in which the silver and copper contents are respectively from 72 to 85 per cent. and from 15 to 28 per cent. The preferred ratio of silver to copper is '72 to 28 per cent. Thorium, barium or one of the alkaline earth metals may be added in amounts amounting to as much as five per cent. of the total alloy. Thus, for example, a preferred composition would comprise 68.4 per cent. silver, 26.6 per cent. copper and five per cent. thorium. This alloy material is used for the main electrodes and for the auxiliary or starting electrodes of the arc rectifier, or at least as much of the main electrodes and the auxiliary electrodes as are subject to the deterioration due to the effect of the arc discharge.

It furthermore has been found that the use of 5 this alloy is advantageous in switch contacts and for the electrodes: of spark gaps. In providing switch contacts of this allot it has been found that the switches resist welding under heavy initial inrushes of current and that they do not pit 10 nor deteriorate readily.

It has been found, for example, that the use of a substantially eutectic silver-copper alloy having a five per cent. amount of thorium has extended the life of the electrodes by ten times the life of a similar pure eutectic silver-copper alloy.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electrode for are discharge valves containing up to five per cent. thorium, the remainder consisting substantially of metal from the group silver and copper.

2. An electrode for are discharge valves containing about five per cent. barium, the remainder consisting substantially of metal from the group silver and copper.

3. An electrode for are discharge valves containing up to five per cent. thorium, the remainder consisting substantially of metal from the group silver and copper in the ratio of 72 to 28.

4. An electrode for arc discharge valves containing up to five per cent. barium, the remainder consisting substantially of metal from the group silver and copper in the ratio of '72 to 28.

5. An electrode for arc discharge valves consisting of about five per cent. thorium, about 68.4 per cent. silver and about 26.6 per cent. copper.

6. An electrode for are discharge valves con- 40 sisting of about five per cent. barium, about 68.4 per cent. silver, and about 26.6 per cent. copper.

7. An electric conductor for electric valves containing about one to five per cent. thorium or barium, the remainder consisting substantially of metal from the group silver and copper.

8. An electric conductor for electric valves containing about one to five per cent. thorium or barium, the remainder consisting substantially of metal from the group silver and copper in the ratio of '72 to 28.

HUGO J. SEEMANN. 

